Abstract 2285: Comparison of the nCyte Dx and CellSearch systems for CTC enumeration

Introduction: Circulating Tumor Cells (CTCs) have clinical utility for cancer prognosis and monitoring disease. The goal of this study was to compare CTC enumeration by the FDA-approved CellSearch technology to a new technology, the nCyte Dx system by Axon Dx, LLC.

Methods: Duplicate peripheral blood samples from 24 patients with advanced prostate cancer were collected in CellSave tubes as standard of care and submitted for CTC quantification using the CellSearch system at ARUP Laboratories. Following CellSearch testing, a paired sample was sent from ARUP to Axon Dx for nCyte Dx analyses. For every pair of samples, the blood was collected at the same time, but the sample tested by Axon Dx was aged 24 to 72 hours beyond the sample tested with CellSearch. CellSearch identifies CTCs by immunomagnetic capture of EpCAM-postive cells, while nCyte Dx does not incorporate specific CTC enrichment. With nCyte Dx, all PBMCs are isolated via density-based separation in a CPT tube and stained with Axon’s immunofluorescent cocktail (nPac). The cells are drawn down onto semi-porous membranes and placed onto microscope slides. Slides are imaged with the nCyte, a rapid fluorescent scanning instrument, and Axon’s advanced cell finding and analysis software (nAble) facilitates automated CTC detection. Due to the high-quality optical properties of the nCyte, the detected material can be characterized and categorized based on morphology and cellular structure.

Results: CellSearch-derived CTC counts were compared with the enumeration results from the nCyte Dx system. Results were reported per 7.5mL blood for both methods. Bland-Altman analysis demonstrates that CellSearch and nCyte Dx results agreed in 22 of the 24 patient sample sets tested within a 95% confidence interval (CI). For both discrepant samples, the CellSearch count was found to be higher. The nCyte Dx method generally detected more CTCs than CellSearch in the lower enumeration range (<10 CTCs). Because previous data from Axon Dx shows no CTCs detected in healthy patients, this finding may be attributable to increased sensitivity rather than decreased specificity. Differences between the results may also be attributable to the natural variation between duplicate blood draws, best characterized by the Poisson distribution model.

Summary and Conclusions: A comparison of CTC enumeration results using the CellSearch and nCyte Dx platforms was performed using duplicate blood samples from 24 prostate cancer patients. The results reveal high similarity between the two technologies, with 22 of 24 patients (92%) having enumeration results that agreed within a 95% CI. While both technologies deliver similar results, there are notable advantages of the nCyte Dx system over CellSearch, including a lack of bias toward EpCAM positive material. Additionally, the superior image quality of nCyte Dx may limit subjectivity in CTC identification and offer the ability to characterize CTC heterogeneity.

Citation Format: Josefa Andrade, Ramsey Mohl, Stephanie Thomas, John Kearney, Phillip Bernard, Hillary S. Sloane. Comparison of the nCyte Dx and CellSearch systems for CTC enumeration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2285.

Cutaneous T-cell lymphoma (CTCL): Current practices in blood assessment and the utility of T-cell receptor (TCR)-Vβ chain restriction

BACKGROUND

Accurate quantification of malignant cells in the peripheral blood of patients with cutaneous T-cell lymphoma is important for early detection, prognosis, and monitoring disease burden.

OBJECTIVE

We sought to determine the spectrum of current clinical practices; critically evaluate elements of current International Society for Cutaneous Lymphomas (ISCL) B1 and B2 staging criteria; and assess the potential role of T-cell receptor-Vβ analysis by flow cytometry.

METHODS

We assessed current clinical practices by survey, and performed a retrospective analysis of 161 patients evaluated at Yale (2011-2014) to compare the sensitivity, specificity, positive predictive value, and negative predictive value of parameters for ISCL B2 staging.

RESULTS

There was heterogeneity in clinical practices among institutions. ISCL B1 criteria did not capture 5 Yale cohort cases with immunophenotypic abnormalities that later progressed. T-cell receptor-Vβ testing was more specific than polymerase chain reaction and aided diagnosis in detecting clonality, but was of limited benefit in quantification of tumor burden.

LIMITATIONS

Because of limited follow-up involving a single center, further investigation will be necessary to conclude whether our proposed diagnostic algorithm is of general clinical benefit.

CONCLUSION

We propose further study of modified B1 criteria: CD4/CD8 ratio 5 or greater, %CD4(+) CD26(-) 20% or greater, or %CD4(+) CD7(-) 20% or greater, with evidence of clonality. T-cell receptor-Vβ testing should be considered in future diagnostic and staging algorithms.

Comparison of immunofluorescence antibody testing and two enzyme immunoassays in the serologic diagnosis of malaria

BACKGROUND

Serologic testing in malaria has traditionally been done by immunofluorescence antibody testing (IFA), but the use of commercially available enzyme immunoassays (EIAs) has become more widespread.

METHODS

We compared IFA with two commercial EIA kits, the Cellabs Pan Malaria CELISA and the Newmarket Malaria EIA. Seventy-five samples from 74 patients with clinically suspected malaria were examined by both EIA kits. The samples were also examined by IFA (n= 48) and/or Giemsa-stained blood smear (n= 48).

RESULTS

Using a consensus result as a gold standard, the agreement, sensitivity, and specificity were, respectively, as follows: Cellabs EIA 93.2, 95.5, and 92.2%; Newmarket EIA 87.7, 68.2, and 96.1%; and IFA 89.1, 86.4, and 91.7%. Compared to positive Giemsa-stained smears, the sensitivities were as follows: Cellabs EIA 90.9% (10/11), Newmarket EIA 54.5% (6/11), and IFA 100% (11/11). Antinuclear antibody (ANA)-positive sera (n= 11) and rheumatoid factor (RF)-positive sera (n= 11) showed no cross-reactivity with the Newmarket EIA, while the Cellabs EIA yielded positive results in one ANA-positive and two RF-positive sera. Among healthy blood donors (n= 50), the Newmarket EIA showed 100% specificity (50/50) and the Cellabs EIA showed a specificity of 92% (46/50).

CONCLUSIONS

While the Newmarket EIA was a generally more specific assay, it was insufficiently sensitive relative to the IFA and the Cellabs EIA for screening purposes for malaria antibodies. The Cellabs EIA demonstrated the best overall sensitivity and is a reasonable choice as a serodiagnostic tool for malaria. It may also be useful as an adjunct to Giemsa-stained smear examination, to aid in cases of low parasitemia in previously nonimmune individuals.